1. Field of the Invention
The present invention relates to a display device such as a plasma display panel (hereinafter also referred to as PDP), and more particularly to a display device in which color split (or color separation) is difficult to occur and which presents less graininess in images.
2. Description of the Background Art
Trio- (or stripe-) arrangement pixels and delta-arrangement pixels exemplify matrix type displays having pixels arranged in a matrix form. FIGS. 19 and 20 are schematic plan views showing a conventional trio-arrangement pixel PT and a conventional delta-arrangement pixel PD, respectively. Although each including three subpixels (or cells) C for emitting the three primary colors of light, red (R), green (G) and blue (B), respectively, these pixels differ from each other in arrangement of the subpixels C. A subpixel for emitting red, for example, is hereinafter also referred to as xe2x80x9cred subpixelxe2x80x9d.
For ease of comparison, both of the trio-arrangement pixels PT and the delta-arrangement pixels PD respectively adjacent to each other in first and second (in this case, vertical and horizontal) directions v and h are spaced at an equal arrangement interval (hereinafter also briefly referred to as xe2x80x9cintervalxe2x80x9d) (the arrangement interval is indicated by p) or at an equal interval between pixel centers, respectively. The arrangement interval may be different in the first and second directions v and h. The subpixels C included in both of the pixels PD and PT have the same shape and area, each of which is rectangular with dimensions of (p/2) and (p/3) in the first and second directions v and h, respectively.
As shown in FIG. 19, in a display device 100T having the trio-arrangement pixels PT, red, green and blue subpixels C are arranged in this order in the second direction h, and subpixels C for the same luminous color are arranged in the first direction v. Particularly, components of the interval between adjacent subpixels C in the display device 100T are p and (p/3) in the first and second directions v and h, respectively. In this case, subpixels C in each pixel PT are aligned in a row in the second direction h, and pixels PT adjacent to each other either in the first or second direction v or h have the same subpixel arrangement.
On the other hand, as shown in FIG. 20, the red, green and blue subpixels C are arranged in the form of a delta (xcex94) in each pixel PD. In the whole display of a display device 100D having delta-arrangement pixels PD, the red, blue and green subpixels C are arranged in this order in the second direction h, and subpixels C for the same luminous color are arranged in the first direction v. Particularly, components of the interval between adjacent subpixels C in the display device 100D are (p/2) and (p/3) in the first and second directions v and h, respectively.
In each delta-arrangement pixel PD, a subpixel C (for green, in this case) present singly in the second direction h is called xe2x80x9csingle subpixelxe2x80x9d and two subpixels C (for red and blue, in this case) aligned adjacently in the second direction h are called xe2x80x9cpaired subpixelsxe2x80x9d. It is possible to consider that the single subpixel C and the paired subpixels C are arranged alternately at an interval of (p/2) in the first direction v.
In the whole display of the display device 100D, pixels PD having the same subpixel arrangement are arranged adjacently in the first direction v. In the second direction h, two types of pixels PD are aligned alternately in which the single subpixel C and the paired subpixels C are arranged in reversed positions to each other in the first direction v.
In general, trio-arrangement pixels PT have good linearity both in the first and second directions v and h in spite of low resolution for the number of pixels, which are thus suitable for figure drawing. On the other hand, delta-arrangement pixels PD, whose adjacent subpixels C are spaced at an interval of (p/2) in the first direction v, generally have high resolution for the number of pixels, whereas being inferior to the pixels PT in linearity both in the first and second directions v and h. Since the pixels PT and PD both have advantages and disadvantages in display quality as described above, either of them is selected generally depending on images to be displayed or personal preference.
Japanese Patent Application Laid-Open No. 2000-357463, for example, discloses a basic configuration as an example of application of delta-arrangement pixels PD to a plasma display panel (PDP).
Further, as one application of such configuration, Japanese Patent Application Laid-Open No. 2000-298451 discloses a method of driving two data electrodes (W electrode) in common (hereinafter also referred to as xe2x80x9cW electrode common address driving methodxe2x80x9d). With this method, circuit costs can be reduced.
As another application, Japanese Patent Application Laid-Open No. 2001-135242 discloses a method of distributing sustain discharge current paths (hereinafter also referred to as xe2x80x9ccurrent distributing methodxe2x80x9d). With this method, a peak current value in discharge current can be reduced, resulting in reduced circuit costs.
As described above, applications of delta-arrangement pixels PD to a PDP create the above-described various advantages which are not attainable by trio-arrangement pixels PT.
However, conventional delta-arrangement pixels PD have a problem of visibility in that xe2x80x9ccolor split (or color separation)xe2x80x9d easily occurs as compared to conventional trio-arrangement pixels PT.
The narrowest visual angle that a man of visual acuity of 1.0 can resolve is one minute angle. In a display device such as a PDP or CRT, one pixel is divided into three subpixels in area, to which the three primary colors, red, green and blue are assigned, respectively. These three subpixels are simultaneously illuminated, to thereby display white. However, when a visual angle between subpixels exceeds one minute angle, an observer sees the three colors splittingly (or separately) and becomes incapable of recognizing one pixel as white. Such phenomenon that the colors are seen splittingly (or separately) is called xe2x80x9ccolor split (or color separation)xe2x80x9d. This color split depends on an observation distance and may become more significant as a display (therefore, a pixel) is observed from a nearer position.
The visual angle between subpixels C is assumed to be equal to the arrangement interval between the subpixels C when viewed from the same distance. Regardless of whether in the same pixel or between adjacent pixels, a minimum value of the interval between the subpixels C for the respective luminous colors (or distance between pixel centers) greatly affects color split. As shown in FIG. 19, in each pixel PT, the minimum value of the interval between the subpixels C (or the minimum value of the distance between the pixel centers) is 0.33 p. On the other hand, as shown in FIG. 20, the above minimum value is 0.6 p in each pixel PD. Accordingly, the minimum value between the pixel centers of the subpixels C in the pixels PD is substantially twice that in the pixels PT. Thus, color split easily occurs in the pixels PD as compared to the pixels PT.
Further, the conventional delta-arrangement pixels PD have another problem of visibility of presenting xe2x80x9cgraininessxe2x80x9d more than in the conventional trio-arrangement pixels PT. This phenomenon easily occurs when black layers are provided in non-display areas NC (see FIGS. 19 and 20) between the subpixels C.
An object of the present invention is to provide a display device in which color split is difficult to occur and which presents less graininess in images.
According to the present invention, the display device includes a plurality of pixels aligned in a first direction and a second direction perpendicular to the first direction and arranged as a whole in a matrix form in a plan view, the plurality of pixels each including first to third subpixels arranged in the form of a delta in the plan view.
In the display device, expressions: pv1=pv2=pv/2; pv3=0; and ph1=ph2 less than ph/3 hold where: components of an arrangement interval between the plurality of pixels in the first and second directions are indicated by pv and ph, respectively; with respect to each of the plurality of pixels, components of the arrangement interval between the first and second subpixels in the first and second directions are indicated by pv1 and ph1, respectively; components of the arrangement interval between the second and third subpixels in the first and second directions are indicated by pv2 and ph2, respectively; and a component of the arrangement interval between the first and third subpixels in the first direction is indicated by pv3.
Further, expressions: pv4=pv/2; pv5=0; and ph4 greater than ph/3 hold where: with respect to first and second subpixels among the plurality of pixels adjacent to each other in the second direction, components of the arrangement interval between the third subpixel of the first pixel and the first subpixel of the second pixel in the first and second directions are indicated by pv4 and ph4, respectively; and a component of the arrangement interval between the second subpixel of the first pixel and the first subpixel of the second pixel in the first direction is indicated by pv5.
Further, adjacent ones of the plurality of pixels in the first direction have the same arrangement of the first to third subpixels.
In the display device, the minimum value of the arrangement interval between the first to third subpixels is smaller than that of the arrangement interval between three subpixels in conventional delta-arrangement pixels. Thus, color split is difficult to occur where the first to third subpixels display, for example, red, green and blue, respectively. Further, since the component of the arrangement interval between the second subpixel and the first and third subpixels in the first direction is equal to that in the conventional delta-arrangement pixels, the display device according to the present invention achieves high resolution for the number of pixels.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.